The invention relates to an apparatus for detecting at least one predetermined angular position on rotating devices, having a tachogenerator with a stator part and a rotor part for producing a tacho signal with speed-dependent frequency, the stator part and rotor part of the tachogenerator forming at least four circumferentially, substantially equidistantly spaced pole areas.
Tachogenerators of the above type are known (pending application U.S. Ser. No. 166,806, filed July, 1979). However, they do not make it possible to supply, in addition to the tacho signal, angular position signals for a plurality of angular positions, which is smaller than the number of tacho signals pulses occurring during each complete revolution. However, it is often necessary to detect or recognise one or more predetermined relative positions between the stator and the rotor. It is then necessary to use a normally optical or magnetic angle indicator, in addition to the tachogenerator. This leads to relatively costly, but imprecisely operating devices.